GooglePlayGames plugin path not correct?

I'm using the GooglePlayGames plugin from GitHub after having no luck with the Prime31 Plugin.

Everything works perfect on a new project but on my existing game the "using GooglePlayGames;" and "Using GooglePlayGames.BasicApi;" register in red in MonoDevelop as if the path can not be found. I have the folder in assets. I have also compared the contents of the plugin to the working version in my other project to ensure something wasn't missed during the import and both appear to have the same content and location.

I have also tried moving the GooglePlayGames folder to plugins and plugins/android but this did not help MonoDevelop with recognition.

Does anyone have suggestions?